Determining the parameters of the Minimal Supergravity Model from 2l + E_T^{miss} + (jets) final states at LHC

We analyse the events with two same-flavour, opposite-sign leptons + $E_T^{miss}$ + (jets) as expected in pp collisions at LHC within the framework of the minimal Supergravity Model. The objective is the determination of the parameters m_0 and m_{1/2} of this model (for a given value of $\tan \beta$). The signature $l^{+}{l}^{-}+E_T^{miss}$ + (jets) selects the leptonic decays of ${\tilde{\chi }}_2^0$, ${\tilde{\chi }}_2^0\to {\tilde{\chi }}_1^0{l}^{+}{l}^{-}$, $\tilde{\chi}^0_2 \to \tilde{l}{L,R}^{\pm} l^{\mp} \to \tilde{\chi}^0_1 l^+ l^-$. We exploit the fact that the invariant dilepton mass distribution has a pronounced structure with a sharp edge at the kinematical endpoint even in such an inclusive final state over a significant part of parameter space. We determine the domain of parameter space where the edge is expected to be visible. We show that a measurement of this edge already constrains the model parameters essentially to three lines in the ($m_0,m_{1\mathrm{/}2}$) parameter plane. We work out a strategy to discriminate between the three-body leptonic decays of ${\tilde{\chi }}_2^0$ and the decays into sleptons ${\tilde{l}}_{L,R}$. This procedure may make it possible to get information on SUSY particle masses already with low luminosity, L{int}=10^3 pb^{-1}.